Fluorescent dyes are widely used in biological research and medical diagnostics. Fluorescent dyes are superior to conventional radioactive materials because fluorescent dyes are typically sufficiently sensitive to be detected, less expensive and less toxic. In particular, a diversity of fluorophores with a distinguishable color range has made it more practical to perform multiplexed assays capable of detecting multiple biological targets in parallel. The ability to visualize multiple targets in parallel is often required for delineating the spatial and temporal relationships amongst different biological targets in vitro and in vivo. In addition, the generation of a wide range of fluorescent dyes has opened a new avenue for conducting high-throughput and automated assays, thus dramatically reducing the unit cost per assay. Moreover, the low toxicity of fluorescent dyes provides ease of handling in vitro, and also renders it safer for imaging biological activities in vivo.
Despite the various advantages of fluorescent dyes, there remains a need for dyes with properties that are well suited for use in modern instrumentation and in various applications. For example, a high quantum yield is generally desired when used in conjunction with common and commercially available laser excitation sources, and there remains a need for dyes which are capable of being excited.